Use of imaging sensors in vehicle imaging systems is common and known. Examples of such known systems are described in U.S. Pat. Nos. 5,949,331; 5,670,935 and/or 5,550,677, which are hereby incorporated herein by reference in their entireties.
In a surround view system, cameras are mounted on front, rear, left and right side of the vehicle, and images from all four (or more) cameras are stitched to generate a top-view/bowl-view/3D view or the like. The quality of stitching of the images for display is generally poor due to offsets in camera actual position and orientation after assembly and installation of the system. Stitching quality is improved by calibrating extrinsic parameters of all cameras (using offline or online calibration methods). A metric is typically desired to have the online objective evaluation of stitching quality and this metric can be used as an output for the user, as well as an input for further improving the stitching quality.
To calibrate the cameras, the subject vehicle may be placed on a flat surface with pre-defined target laid over the stitching region(s). Images of the target are captured by the cameras and are analyzed in the top view to get a metric or confidence value for stitching quality. In some cases, the camera is calibrated in such a way to achieve best stitching quality offline.